In the past, decorative light strings used a plurality of series or parallel connected incandescent lights. To make one or more of them flash or twinkle, a bimetallic strip was used to either respectively open circuit or short out the filament, or a partial resistive shunt would be applied across the light terminals with a switching circuit to dim or in effect extinguish the bulb.
These dimming circuits were typically not polarity sensitive so they could operate effectively on AC circuits.
With the advent of low cost Light Emitting Diodes (LEDs) especially when they became available in different colors, have caused the decorative light industry to move toward these lower wattage, lower temperature devices. Unfortunately, the circuitry for creating light effects such as flashing, twinkling, shimmering, color changing (such as for LEDs which change color upon application of different voltages or polarities), or the like require more sophisticated controllers to achieve what previously could be done with simple electromechanical solutions.
Furthermore, LED devices are essentially rectifiers in series or parallel which results in problematic results for other devices which require full wave DC when the LEDs on an AC circuit create half wave rectification.
If an LED is removed from the circuit, there are known methods for maintaining the rest of the string illuminated but these methods can sometimes interfere with other features of the light string.
Finally, cost is a critical factor. Whatever solution is required to make the transition from incandescent to LED lighting must maintain the low cost nature of incandescent bulbs.
The present invention addresses these issues.